Efficient DL OFDMA frequency selectivity harvesting

ABSTRACT

A method for communication in a wireless local area network comprises receiving a frame at a first device, the frame being transmitted by a second device. The method further comprises determining, by the first device using the frame, a channel strength for each of a plurality of sub-bands associated with a bandwidth of the frame. A sub-band of the plurality of sub-bands is selected based on the channel strength determinations made using the frame. The first and second devices communicate using the selected sub-band.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/818,214, filed on Aug. 4, 2015, now U.S. Pat. No. 9,907,073, issuedFeb. 27, 2018, which claims the benefit of U.S. Provisional ApplicationNo. 62/089,121, filed on Dec. 8, 2014, U.S. Provisional Application62/107,963, filed on Jan. 26, 2015, and U.S. Provisional Application62/112,095, filed on Feb. 4, 2015, the entire respective contents ofwhich are incorporated herein by reference.

BACKGROUND 1. Technical Field

The technology described herein relates generally to wirelessnetworking. More particularly, the technology relates generally toallocating frequency resources to each of a plurality of stations (STAs)in a Wireless Local Area Network (WLAN).

2. Description of the Related Art

A WLAN is being standardized by the IEEE (Institute of Electrical andElectronics Engineers) Part 11 under the name of “Wireless LAN MediumAccess Control (MAC) and Physical Layer (PHY) Specifications.” A seriesof standards have been adopted as the WLAN evolved, including IEEE Std802.11™-2012 (March 2012). The IEEE Std 802.11™-2012 was subsequentlyamended by IEEE Std 802.11ae™-2012, IEEE Std 802.11aa™-2012, IEEE Std802.11ad™-2012, and IEEE Std 802.11ac™-2013. These standards are eachhereby incorporated by reference herein in their entirety.

Recently, a high efficiency WLAN for enhancing system throughput inhigh-density scenarios is being developed by the IEEE 802.11ax taskgroup. In such WLAN scenarios, a transmitting device may transmit anOrthogonal Frequency Division Multiple Access (OFDMA) frame havingrespective data for each of a plurality of receiving devices. Within theOFDMA frame, the respective data for the receiving devices may betransmitted in one more frequency region (sub-bands) respectivelyallocated to the receiving devices. Each sub-band includes a pluralityof subcarriers at different frequencies.

The respective channels between the transmitting device and each of thereceiving devices may be frequency selective, which means the channelmagnitude changes over frequency. In the design of an OFDMA wirelessnetwork, it is possible to take advantage of the frequency selectivityof the channel. For instance, the transmitting device can scheduledownlink (DL) transmission for several receiving devices within adownlink OFDMA PHY Protocol Data Unit (PPDU), where the informationrelated to each receiving device is placed in the sub-band wherein thereceiving device experiences higher channel magnitude.

The sub-bands that have a high channel magnitude for each receivingdevice may be determined in order to use sub-bands optimally.

SUMMARY

A method for communication in a wireless local area network comprisesreceiving a frame at a first device, the frame being transmitted by asecond device, and determining, by the first device using the frame, achannel strength for each of a plurality of sub-bands associated with abandwidth of the frame. The first and second devices communicate using asub-band selected from the plurality of sub-bands, the sub-band beingselected based on the channel strength determinations made using theframe.

In an embodiment, the first and second devices are part of a BasicService Set (BSS), and the frame is an Orthogonal Frequency DivisionMultiplexing (OFDM) frame including an indication that the channelstrengths are to be determined using the frame.

In an embodiment, the frame is a pre-announced frame, and the methodfurther comprises receiving an announcement frame by the first deviceprior to receiving the pre-announced frame. The announcement frameindicates that the channel strengths are to be determined using thepre-announced frame.

In an embodiment, the announcement frame includes a Null Data PacketAnnouncement (NDPA) frame, and a Sounding Dialog Token field of the NDPAframe indicates that the channel strengths are for use in a subsequentOFDMA frame exchange.

In an embodiment, the first and second devices are part of a BasicService Set (BSS), the first device being a station and the seconddevice being an access point, and the announcement frame includes anindication that a group of one or more devices associated with the BSSare to determine respective channel strengths using the pre-announcedframe.

In an embodiment, the announcement frame includes an indication ofwhether the first device is to transmit a report prepared according tothe determined channels strengths in response to the pre-announced frameor transmit the report in response to a poll frame, or an indicationthat the report may be included in a field of a Medium Access Control(MAC) header of a subsequent frame transmitted by the first device.

In an embodiment, the announcement frame includes an indication ofwhether the first device is to transmit a report prepared using anaverage of channel strengths for a sub-band across multiple transmittingantennas, multiple receiving antennas, or combinations of multipletransmitting antennas and multiple receiving antennas.

In an embodiment, the method further comprises transmitting a sub-bandchannel state information (CSI) report indicating the channel strengthfor each of a set of sub-bands of the plurality of sub-bands to thesecond device by the first device. The selected sub-band is based on thesub-band CSI report received by the second device.

In an embodiment, the method further comprises transmitting a sub-bandchannel state information (CSI) report including a combined strengthdetermined using channel strengths of the plurality of sub-bands. Theselected sub-band is based on the combined strength.

In an embodiment, the method further comprises transmitting a sub-bandchannel state information (CSI) report including a channel strengthmeasure determined using channel strengths of the plurality ofsub-bands. The selected sub-band is based on the channel strengthmeasure.

In an embodiment, the method further comprises transmitting a sub-bandchannel state information (CSI) report including a first channelstrength of the channel strengths for the sub-bands only when the firstchannel strength is greater than a second channel strength of thechannel strengths for the sub-bands, the first channel strengthsatisfies a predetermined criteria, the predetermined criteria relatingto one or more of a Received Signal Strength Indication (RSSI), a Signalto Interference and Noise Ratio (SINR), a Modulation and Coding Scheme(MCS), and a Number of Spatial Streams (NSS), or a previous framereceived from the second device includes an indication that the sub-bandCSI report is to include the first channel strength.

In an embodiment, the method further comprises determining a sub-bandchannel state information (CSI) report according to one or more of thechannel strengths, receiving, by the first device, a polling frame, andtransmitting the sub-band CSI report in response to the polling frame.

In an embodiment, the method further comprises determining a sub-bandchannel state information (CSI) report according to one or more of thechannel strengths, and transmitting the sub-band CSI report in responseto the frame.

In an embodiment, the method further comprises determining a sub-bandchannel state information (CSI) report according to one or more of thechannel strengths, and transmitting the sub-band CSI report in a fieldof a High Throughput (HT) Control field of a Medium Access Control (MAC)frame.

In an embodiment, the method further comprises determining a sub-bandchannel state information (CSI) report according to one or more of thechannel strengths, and transmitting the sub-band CSI report in amanagement frame including an indication that the management frameincludes the sub-band CSI report. The management frame is an Actionframe or an Action No ACK frame.

In an embodiment, the frame is a beacon frame transmitted by the seconddevice.

In an embodiment, the frame is a Power Save (PS)-Poll frame or a Qualityof Service (QoS) Null frame.

In an embodiment, the bandwidth is a widest allowed bandwidth, thewidest allowed bandwidth being a maximum bandwidth that can be receivedby the second device, transmitted by the first device, and sensed by thefirst and second devices during active channel sensing.

In an embodiment, the frame is an ACK frame or a Block ACK (BA) frame.

In an embodiment, the frame is transmitted in response to an indicationincluded in a preceding unicast frame transmitted by the second device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless network according to an embodiment.

FIG. 2 illustrates a schematic block diagram of a wireless deviceaccording to an embodiment.

FIG. 3 illustrates an Orthogonal Frequency Division Multiplexing (OFDM)frame that may be employed in an embodiment.

FIG. 4 illustrates an Orthogonal Frequency Division Multiple Access(OFDMA) frame that may be employed in an embodiment.

FIG. 5 illustrates a sequence of frames including a plurality of OFDMAframes according to an embodiment.

FIG. 6A illustrates a process for communicating using an OFDMA frameaccording to an embodiment.

FIG. 6B illustrates a process for communicating using an OFDMA frameaccording to an embodiment.

FIG. 7 illustrates a process of determining OFDMA sub-band CSI in astation according to an embodiment.

FIG. 8 illustrates an Access Point (AP) initiated channel soundingprocess according to another embodiment.

FIG. 9 illustrates a format of a Null Data Packet Announcement (NDPA)frame according to an embodiment.

FIG. 10 illustrates a format of an NDPA frame according to anotherembodiment.

FIG. 11 illustrates a format of an NDPA frame according to anotherembodiment.

FIG. 12 illustrates a format of an NDPA frame according to anotherembodiment.

FIG. 13 illustrates a format of a frame for requesting OFDMA sub-bandchannels state information (CSI) according to an embodiment.

FIG. 14 illustrates a format of a Media Access Control (MAC) frameincluding High Efficiency (HE) fields according to an embodiment.

FIG. 15 illustrates a frame format for reporting OFDMA sub-band CSIaccording to an embodiment.

FIG. 16 illustrates an AP-initiated channel sounding process accordingto another embodiment.

FIG. 17 illustrates a process of determining OFDMA sub-band CSI in astation according to another embodiment.

FIG. 18A illustrates a station-initiated OFDMA sub-band sounding processaccording to an embodiment.

FIG. 18B illustrates a station-initiated OFDMA sub-band sounding processaccording to an embodiment.

FIG. 19 illustrates a format of a frame used in a station-initiatedOFDMA sub-band sounding process according to an embodiment.

FIG. 20 illustrates a station-initiated OFDMA sub-band sounding processaccording to another embodiment.

FIG. 21 illustrates formats of frames used in a station-initiated OFDMAsub-band sounding process according to another embodiment.

FIG. 22 illustrates formats of frames used in a station-initiated OFDMAsub-band sounding process according to another embodiment.

FIG. 23 illustrates a process of determining OFDMA sub-band CSI in an APaccording to an embodiment.

DETAILED DESCRIPTION

In the following detailed description, certain illustrative embodimentshave been illustrated and described. As those skilled in the art wouldrealize, the described embodiments may be modified in various differentways without departing from the spirit or scope of the presentdisclosure. Accordingly, the drawings and description are to be regardedas illustrative in nature and not restrictive. Like reference numeralsdesignate like elements throughout the specification.

FIG. 1 illustrates a wireless network according to an embodiment. Thewireless network includes an infrastructure Basic Service Set (BSS) 100of a Wireless Local Area Network (WLAN). In an 802.11 wireless LAN, theBSS provides the basic building-block and typically includes an accesspoint (AP) and one or more associated stations (STAs). In FIG. 1, theBSS 100 includes an Access Point 102 wirelessly communicating with aplurality of wireless devices (or stations) 104 to 114 (also referred toas AP and STA1 to STAG). The wireless devices may include a mediumaccess control layer (MAC) and a physical layer (PHY) according to anIEEE (Institute of Electrical and Electronics Engineers) 802.11standard.

The AP 102 is a station, that is, a STA, configured to control andcoordinate functions of the BSS 100. The AP 102 may transmit informationto a single station selected from the plurality of stations STA1 to STA6in the BSS 100 using a single frame, or may simultaneously transmitinformation to two or more (e.g., to all six) stations STA1 to STA6 inthe BSS 100 using either a single Orthogonal Frequency DivisionMultiplexing (OFDM) broadcast frame, a single OFDM Multi-UserMulti-Input-Multi-Output (MU-MIMO) transmission, or a single OrthogonalFrequency Division Multiple Access (OFDMA) frame.

The stations STA1 to STA6 may transmit data to the AP 102 using a singleframe, or transmit information to and receive information from anotherone of the stations STA1 to STA6 using a single frame.

In another embodiment, the AP 102 may be absent and the stations STA1 toSTA6 may be in an ad-hoc network.

Each of the stations STA1 to STA6 and the AP 102 includes a processorand a transceiver, and may further include a user interface and adisplay device. The processor is configured to generate a frame to betransmitted through a wireless network, to process a frame receivedthrough the wireless network, and to execute protocols of the wirelessnetwork. The processor may perform some or all of its functions byexecuting computer programming instructions stored on a non-transitorycomputer-readable medium. The transceiver represents a unit functionallyconnected to the processor, and designed to transmit and receive a framethrough the wireless network. The transceiver may be defined using asingle component that performs the functions of transmitting andreceiving, or two separate components each performing one of suchfunctions. The processor and the transceiver may be implemented byhardware components and/or software components integrated within therespective STA1 to STA6 and/or the AP 102.

AP 102 may be or may include a WLAN router, a stand-alone Access Point,a WLAN bridge, a Light-Weight Access Point (LWAP) managed by a WLANcontroller, and the like. In addition, a station such as a personalcomputer or cellular phone may be able to operate as the AP 102, such aswhen a cellular phone is configured to operate as a wireless “hot spot.”

Each of STA1 to STA6 may be or may include a desktop computer, a laptopcomputer, a tablet PC, a wireless phone, a mobile phone, a smart phone,an e-book reader, a Portable Multimedia Player (PMP), a portable gameconsole, a navigation system, a digital camera, a Digital MultimediaBroadcasting (DMB) player, a digital audio recorder, a digital audioplayer, a digital picture recorder, a digital picture player, a digitalvideo recorder, a digital video player, and the like.

The present disclosure may be applied to WLAN systems according to IEEE802.11 standards but is not limited thereto.

In IEEE 802.11 standards, frames exchanged between stations (includingaccess points) are classified into management frames, control frames,and data frames. A management frame may be a frame used for exchangingmanagement information that is not forwarded to higher layer of acommunication protocol stack. A control frame may be a frame used forcontrolling access to a medium. A data frame may be a frame used fortransmitting data to be forwarded to a higher layer of the communicationprotocol stack.

Each frame's type and subtype may be identified using a type field and asubtype field included in a control field of the frame, as prescribed inthe applicable standard.

FIG. 2 illustrates a schematic block diagram of a wireless device 200according to an embodiment. The wireless or WLAN device 200 canrepresent any device in a BSS, e.g., AP 102 or any of stations 104-114in FIG. 1. The WLAN device 200 includes a baseband processor 210, aradio frequency (RF) transceiver 240, an antenna unit 250, a storagedevice (e.g., memory) 232, one or more input interfaces 234, and one ormore output interfaces 236. The baseband processor 210, the memory 232,the input interfaces 234, the output interfaces 236, and the RFtransceiver 240 may communicate with each other via a bus 260.

The baseband processor 210 performs baseband signal processing, andincludes a MAC processor 212 and a PHY processor 222.

In an embodiment, the MAC processor 212 includes a MAC softwareprocessing unit 214 and a MAC hardware processing unit 216. The storagedevice (or memory) 232 may be a non-transitory computer readable mediumthat stores software (e.g., computer programing instructions)hereinafter referred to as “MAC software”. The MAC software processingunit 214 executes the MAC software to implement a first plurality offunctions of the MAC layer. The MAC hardware processing unit 216 mayimplement a second plurality of functions of the MAC layer inspecial-purpose hardware, hereinafter referred to “MAChardware.”However, the MAC processor 212 is not limited thereto. Forexample, the MAC processor 212 may be configured to perform the firstand second plurality of functions entirely in software or entirely inhardware according to implementation.

The PHY processor 222 includes a transmitting signal processing unit 224and a receiving signal processing unit 226. The PHY processor 222implement a plurality of functions of the PHY layer. These functions maybe performed in software, hardware, or a combination thereof accordingto implementation. In an embodiment, the PHY processor 222 may beconfigured to generate channel state information (CSI) according toinformation received from the RF transceiver 240.

The channel state information (CSI) may include one or more of aReceived Signal Strength Indication (RSSI), a Signal to Interference andNoise Ratio (SINR), a Modulation and Coding Scheme (MCS), and a Numberof Spatial Streams (NSS). CSI may be generated for one or more of afrequency block, a sub-band within the frequency block, a subcarrierwithin a frequency block, a receiving antenna, a transmitting antenna,and combinations of a plurality thereof.

The RF transceiver 240 includes an RF transmitter 242 and an RF receiver244. The RF transceiver 240 is configured to transmit first informationreceived from the baseband processor 210 to the WLAN, and provide secondinformation received from the WLAN to the baseband processor 210.

The antenna unit 250 includes one or more antennas. When Multiple-InputMultiple-Output (MIMO) or Multi-User MIMO (MU-MIMO) is used, the antennaunit 250 may include a plurality of antennas.

The input interfaces 234 receive information from a user, and the outputinterfaces 236 output information to the user. The input interfaces 234may include one or more of a keyboard, keypad, mouse, touchscreen, touchscreen, microphone, and the like. The output interfaces 236 may includeone or more of a display device, touch screen, speaker, and the like.

As described herein, many functions of the WLAN device 200 may beimplemented in either hardware or software, and which functions areimplemented in software and which functions are implemented in hardwarewill vary according to constraints imposed on a design. The constraintsmay include one or more of design cost, manufacturing cost, time tomarket, power consumption, available semiconductor technology, and soon.

As described herein, a wide variety of electronic devices, circuits,firmware, software, and combinations thereof may be used to implementthe functions of the components of the WLAN device 200. Furthermore, theWLAN device 200 may include other components, such as applicationprocessors, storage interfaces, clock generator circuits, power supplycircuits, and the like, which have been omitted in the interest ofbrevity.

FIG. 3 illustrates an Orthogonal Frequency Division Multiplexing (OFDM)frame 300 according to an embodiment. The OFDM frame 300 includes a PHYheader 320 and a Physical Layer Convergence Procedure (PLCP) ServiceData Unit (PSDU) 330. The PHY header 320 includes a legacy preamble 302,a Very High Throughput (VHT) first signal (VHT-SIG-A) field 304, a VHTShort Training Field (VHT-STF) 306, a VHT Long Training Field (VHT-LTF)308, and a VHT second signal (VHT-SIG-B) field 310.

The legacy preamble 302 includes Legacy STF (L-STF) and Legacy LTF(L-LTF) fields that include symbols that are used by a receiving deviceto identify the start of the OFDM frame 300, synchronize timers, and, inMIMO-capable equipment, select an antenna. The legacy preamble 302 alsoincludes a Legacy Signal (L-SIG) field that includes information fromwhich a legacy receiving device (for example, a device operatingaccording to IEEE Std 802.11ac™) may determine a data rate and a lengthfor the frame.

The VHT-SIG-A field 304 and VHT-SIG-B field 310 include information thatthe receiver uses to receive the PSDU 312, such as a bandwidthindication, a Space-Time Block Coding (STBC) indication, a Group ID, apartial Association Identifier (AID) field, a Modulation and CodingScheme (MCS) indication, and so on.

The VHT-STF 306 and VHT-LTF 308 fields include symbols that are used bythe receiving device to set receiver gain and to estimate a channelbetween a transmitter of the OFDM frame 300 and the receiving device,respectively.

The PSDU 330 includes data symbols that are used to transport anaggregate MAC Protocol Data Unit (A-MPDU) including one or more MPDUs.The MPDUs in the PSDU 330 are intended either for a single receivingdevice when the OFDM frame 300 is not a broadcast frame, or for all thereceiving devices in a group when the OFDM frame 300 is a broadcastframe wherein all the receiving devices in the group receive the sameinformation.

As can be seen in FIG. 3, the PSDU 330 uses all of the subcarriers usedby the PHY header 320. Therefore, in an embodiment, a frame using a 20MHZ frequency segment includes the PSDU 330 using 56 subcarriers, aframe using a 40 MHZ frequency segment includes the PSDU 330 using 114subcarriers, a frame using a 80 MHZ frequency segment includes the PSDU330 using 242 subcarriers, and a frame using a 160 MHZ frequency segmentor two 80 MHz frequency segments includes the PSDU 330 using 484subcarriers.

FIG. 4 illustrates an Orthogonal Frequency Division Multiple Access(OFDMA) frame 400 such as may be transmitted in an embodiment. The OFDMAframe 400 includes a PHY header 410 and first, second, third, and fourthPSDUs 412, 414, 416, and 418.

The PHY header 410 includes a legacy preamble 402, a High Efficiency(HE) signal portion 404, an HE Short Training Field (HE STF) 406, and anHE Long Training Field (HE LTF) 408. Unlike the PHY header 320, the PHYheader 410 includes an indication that the OFDMA frame 410 is an OFDMAframe, or in some embodiments, there would be an indication whether theframe is a single-user (SU) or a multi-user (MU) frame.

The High Efficiency (HE) signal portion 404 includes an HE signal A (HESIG-A) field, which is transmitted using one or more symbols, and an HEsignal B (HE SIG-B) field, which is transmitted using one or moresymbols. The HE SIG-A field and HE SIG-B field include information thatthe receiver uses to receive the first, second, third and fourth PSDUs412, 414, 416, and 418. In an embodiment, a single HE SIG-A field may beduplicated across a plurality of frequency blocks and may containinformation common to all of the first, second, third and fourth PSDUs412, 414, 416, and 418. In an embodiment, the HE SIG-B field includes aunique sub-field for each of the first, second, third and fourth PSDUs412, 414, 416, and 418. In an embodiment, the HE SIG-B field may have avariable length.

The HE STF 406 and HE LTF 408 fields include symbols that are used bythe receiving device to set receiver gain and to estimate a channelbetween a transmitter of the OFDMA frame 400 and the receiving device,respectively.

The first, second, third and fourth PSDUs 412, 414, 416, and 418 occupyrespective sub-bands within the frequency segment used by the OFDMAframe 400, each sub-band including a contiguous plurality ofsubcarriers. Each of the first, second, third and fourth PSDUs 412, 414,416, and 418 includes data symbols that are used to transport A-MPDUsincluding one or more MPDUs.

The MPDUs in each of the first, second, third and fourth PSDUs 412, 414,416, and 418 may each be intended for a different receiving device,respectively. FIG. 4 illustrates the first, second and fourth PSDUs 412,414, 416, and 418 associated with first through fourth stations STA1through STA4, respectively. However, embodiments are not limitedthereto.

In an embodiment, of the OFDMA frame 400 using a 20 MHZ frequencysegment may include 9 PSDUs, the OFDMA frame 400 using a 40 MHZfrequency segment may include 18 PSDUs, the OFDMA frame 400 using a 80MHZ frequency segment may include 36PSDUs, and the OFDMA frame 400 usinga 160 MHZ frequency segment or two 80 MHZ frequency segments may include72 PSDUs.

FIG. 5 illustrates a sequence of frames according to an embodiment,illustrating an association of PSDUs with receiving devices (e.g., thestations STA1 to STA6 of FIG. 1). The sequence of frames includes afirst OFDMA frame 500, a first acknowledgement (ACK) frame 530, a secondOFDMA frame 540, and a second ACK frame 570. In an embodiment, each ofthe frames uses a 20 MHZ frequency segment, and the first and secondOFDMA frames 500 and 540 each include nine sub-bands within the 20 MHzfrequency segment (where considering the guard-bands in each side, eachsub-channel would be 2 MHz.)

The first OFDMA frame 500 includes a PHY header 510 substantiallysimilar to the PHY header 410 of FIG. 4. The first OFDMA frame 500further includes first through ninth sub-bands 512 through 528, eachincluding a contiguous plurality of subcarriers.

In the first OFDMA frame 500, the first and second sub-bands 512 and 514are used to transport information to a first station STA1. The third,fourth, and fifth sub-bands 516, 518, and 520 are used to transport datato second, third, and fourth stations STA2, STA3, and STA4,respectively. The sixth and seventh sub-bands 522 and 524 are used totransport information to a fifth station STA5. The eighth and ninthsub-bands 526 and 528 are used to transport information to a sixthstation STA6.

The first OFDMA frame 500 is followed by one or more first ACK or BlockACK (BA) frames 530.

In the example of FIG. 5, at some time after the first OFDMA frame 500is transmitted, the second OFDMA frame 540 is transmitted. Like thefirst OFDMA frame 500, the second OFDMA frame 540 includes a PHY header550 substantially similar to the PHY header 410 of FIG. 4 and firstthrough ninth sub-bands 522 through 568, each including a contiguousplurality of subcarriers. The second OFDMA frame 540 may use the same 20MHz frequency segment that was used by the first OFDMA frame 500.

The allocation of sub-bands to stations in the second OFDMA frame 540could be different from the allocation of sub-bands to stations in thefirst OFDMA frame 500. In the second OFDMA frame 540, the first andsecond sub-bands 552 and 554 are again used to transport information toa first station STA1, and the fourth and fifth sub-bands 558 and 560 areagain used to transport data to third and fourth stations STA3 and STA4,respectively.

However, unlike in the first OFDMA frame 500, in the second OFDMA frame540, the sixth and seventh sub-bands 562 and 564 are used to transportinformation to a seventh station STAT, the ninth sub-band 568 is used totransport information to an eighth station STA8, and the third and eightsub-bands are not used.

The second OFDMA frame 540 is followed by one or more second ACK or BAframes 570.

FIGS. 6A and 6B illustrates a process 600 for communicating using anOFDMA frame according to an embodiment. In the illustrated example, aBSS (e.g. the BSS 100 of FIG. 1) includes an AP and first, second, andthird OFDMA-capable stations STA1, STA2, and STA3.

At S610, for each of the stations STA1, STA2, and STA3, the APdetermines sub-band channel state information (CSI) for a plurality ofsub-bands of a bandwidth available for OFDMA communication between theAP and the stations STA1, STA2, and STA3. In an embodiment, thebandwidth is a widest available bandwidth that can be transmitted acrossits entirety by the AP, received across its entirety by the stations inthe BSS, and sensed across its entirety by channel sensing methods, forexample, using Clear Channel Assessment (CCA).

In an embodiment, determining the sub-band CSI at S610 includes asounding process such as the sounding process 612 shown in FIG. 6B.However, embodiments are not limited thereto.

In the sounding process 612, at S614 the AP transmits a sounding frameOFDM_DF to be used for OFDMA sub-band sounding to the stations STA1,STA2, and STA3, e.g., to all the stations associated within the BSS. Theframe OFDM_DF is an OFDM downlink frame in an implementation. The frameOFDM_DF may be transmitted at the widest allowable bandwidth.

In an embodiment, the frame OFDM_DF includes an indication that OFDMAsub-band sounding is to be performed using the frame OFDM_DF. In anotherembodiment, the indication that OFDMA sub-band sounding is to beperformed using the frame OFDM_DF is based on previously providedinstruction, e.g., as part of a previous frame transmitted by the AP oras part of communication protocol policy when the stations were firstassociated with the AP to form a particular BSS. In another embodiment,whether to perform OFDMA sub-band sounding using the frame OFDM_DF isdetermined according to a preconfigured internal policy of a stationreceiving the frame OFDM_DF.

In some embodiments, the OFDM_DF frame could be any of the frames thatthe AP sends as part of its regular functions, such as a broadcastframes (e.g., Beacon frames), a normal data carrying frame (to a set ofSTAs) or a control frame (that possibly polls a set of STAs to send ULframes such as a Trigger frame), and all or a subset of the STAs thatare addressed by the OFDM_DF frame performs the required processing fordetermining CSI on that frame. In some embodiments, the OFDM_DF framemay be an NDP frame or may be a pre-announced frame preceded by anannouncement frame (for example, an NDP frame preceded by a NDPAnnouncement (NDPA) frame.)

In an embodiment, all stations receiving frame OFDM_DF perform OFDMAsub-band sounding using the frame OFDM_DF. In another embodiment, theframe OFDM_DF includes an indication of which stations are to performOFDMA sub-band sounding. The indication may include one or moreaddresses or identifiers respectively corresponding to stations in theBSS (such as, for example, all or a portion of one or more AssociationIDs (AIDs)), an identifier of a previously established group of stationsin the BSS, or an indication corresponding to all of the stations in theBSS. The group identification would be based on a prior announcedgroup-membership that associated a set of STAs with a single identifier.

In an embodiment, the frame OFDM_DF may further include parameters foruse in determining and reporting the OFDMA sub-band CSI. The parametersmay include one or more of a bandwidth resolution and an indication ofone or more sub-bands to be reported on or not reported on. Some or allof these parameters in general might be specific to each STA, and somecould be generally specified for all the STAs.

In another embodiment, the indication of which stations are to performOFDMA sub-band sounding, the parameters for use in determining andreporting the OFDMA sub-band CSI, or both may be included in a previousframe broadcast by the AP that indicated that the OFDMA sub-bandsounding was to be performed (e.g., an NDPA frame).

The stations STA1, STA2, and STA3 each determines respective OFDMAsub-band CSI using the frame OFDM_DF, e.g., to process and obtain RSSI,SINR, MCS, and NSS per sub-band or set of sub-bands for each of AP'stransmitting antennas with respect to each station's receiving antennas.In an embodiment, the stations STA1, STA2, and STA3 determine the OFDMAsub-band CSI using the LTF symbols (e.g., VHT LTF or HE-LTF symbols) ofthe frame OFDM_DF.

At S616, the first station STA1 transmits a first OFDMA sub-band CSIreport frame CSI1 to the AP. The first OFDMA sub-band CSI report frameCSI1 is a report transmitted in response to the OFDM_DF frame of S614,and includes OFDMA sub-band CSI determined by the first station STA1according to the frame OFDM_DF of S614. In an embodiment, each stationsends their respective CSI report frame unsolicited, e.g., according tocarrier sense multiple access with collision avoidance (CSMA/CA)protocol. Alternatively, each station may send the respective CSI reportframe whenever the AP sends a request. In some embodiments, the sub-bandCSI report may be included as additional fields and sub-fields in a dataframe that a STA sends to the AP. In some embodiments, the sub-band CSIreport may be included in a management frame sent to the AP.

In an embodiment, the OFDMA sub-band CSI report frame may be a MAC frameincluding the OFDMA sub-band CSI in a High Efficiency Control Extension(HECE) field of a High Throughput Control (HT Control) field. In anembodiment, the OFDMA sub-band CSI report frame may be an Action orAction No ACK frame including an Action field indicating that the frameis an OFDMA sub-band CSI report frame.

At S618, the second station STA2 transmits a second OFDMA sub-band CSIreport frame CSI2 to the AP. The second OFDMA sub-band CSI report frameCSI2 includes OFDMA sub-band CSI determined by the second station STA2according to the frame OFDM_DF of S614. The second station STA2 may sendthe CSI report frame either unsolicited or whenever the AP sends arequest.

At S620, the third station STA3 transmits a third OFDMA sub-band CSIreport frame CSI3 to the AP. The third OFDMA sub-band CSI report frameCSI3 includes OFDMA sub-band CSI determined by the third station STA3according to the frame OFDM_DF of S614. The third station STA3 may sendthe CSI report frame either unsolicited or whenever the AP sends arequest.

Returning to FIG. 6A, at S630 the AP determines an allocation ofsub-bands to stations in the BSS according to the information includedin the first, second, and third OFDMA sub-band CSI report frames CSI1,CSI2, and CSI3.

In an embodiment, allocating sub-bands to stations includes determininga number of sub-bands to allocate to each station, and assigningsub-bands to each station until the allocated number of sub-bands in thechannel is assigned to each station. Each sub-band may be assigned to astation, from among the stations having less than the allocated numberof sub-bands currently assigned to them, for which the sub-band has themost suitable CSI, e.g., a highest channel magnitude or among thesub-bands with highest channel magnitude.

In some embodiments, the AP may be configured to use other processes forallocating sub-bands to stations according to the sub-band CSI for eachstation, such as water filling, call admission control, and the like.

At S650, the AP prepares an OFDMA frame OFDMA_F including first, second,and third information intended for delivery to the first, second, andthird stations STA1, STA2, and STA3, respectively. The first to thirdinformation may include data from buffers within the AP, each bufferbeing respectively associated with an intended station of the first tothird stations STA1 to STA3. The first information is disposed in one ormore sub-bands assigned to the first station STA1, the secondinformation is disposed in one or more sub-bands assigned to the secondstation STA2, and so on.

At S670, the AP transmits the OFDMA frame OFDMA_F to the stations STA1,STA2, and STA3 according to the sub-band allocation performed in S650.

FIG. 7 illustrates a process 700 of determining OFDMA sub-band CSI in astation (e.g., STA1, STA2, or STA3) according to an embodiment.

At S704, the station measures one or more characteristics of a channelbetween a transmitter of a downlink (DL) frame, such as an AP, and thestation. The station measures the channel characteristics using one ormore fields of the DL frame, such as, for example, a Very HighThroughput Long Training Field (VHT-LTF) or HE-LTF symbols.

In an embodiment, the DL frame is an OFDM downlink frame (e.g., OFDM_DFillustrated in FIG. 6B) transmitted using a frequency segment having awidest allowable bandwidth. The widest allowable bandwidth is a widestbandwidth that can be transmitted in its entirety by the transmitter,received across its entirety by the stations in the BSS, and sensed inits entirety by active channel sensing. The widest allowable bandwidthis sometimes constrained by the assessment of the channel at thetransmitter side.

In an embodiment, the DL frame may be a Null Data Packet (NDP). In anembodiment, the DL frame may be a MAC Control frame, a MAC Data frame,or a MAC Management frame.

In an embodiment, the station may measure only some of the sub-bandswithin the frequency segment. The sub-bands to be measured may bedetermined using an indication included in a frame received from the AP,such as a received Null Data Packet Announce (NDPA), Action, or ActionNo ACK frame that include an indication that OFDMA sub-band CSI was tobe determined, or the DL frame.

In an embodiment, the received indication of which sub-bands to measuremay include an indication determined according to a prior allocation ofone or more sub-bands to one or more other stations. In an embodiment,the received indication of which sub-bands to measure may be determinedaccording to prior OFDMA sub-band CSI provided by the station.

In another embodiment, the sub-bands to be measured may be determinedaccording to a policy of the station and previously determinedinformation. The previously determined information may include values ofpreviously determined OFDMA sub-band CSI, which OFDMA sub-band CSI waspreviously reported to the AP, and previously received indications fromthe AP.

The measurements taken for each sub-band may include a Received SignalStrength Indication (RSSI), a Signal to Interference and Noise Ratio(SINR), a Modulation and Coding Scheme (MCS), a Number of SpatialStreams (NSS), and the like. In an embodiment, measurements for each ofa plurality of subcarriers of each sub-band are combined to determine arespective measurement for each sub-band.

The measurements for each sub-band may be taken for each of a pluralityof transmitting antennas when the DL frame is transmitted using theplurality of transmitting antennas. The measurements for each sub-bandmay be taken for each of a plurality of receiving antennas when the DLframe is received using the plurality of receiving antennas. Themeasurements for each sub-band may be taken for each combination of atransmitting antenna and a receiving antenna when the DL frame istransmitted using the plurality of transmitting antennas and receivedusing the plurality of receiving antennas.

At S706, the station determines channel strength measures for eachmeasured sub-band. In an embodiment, the channel strength measures foreach measured sub-band are determined for each transmitting antenna, foreach receiving antenna, and/or for each combination of a transmittingantenna and a receiving antenna.

Determining the channel strength measures for each measured sub-band mayinclude computing a metric using one or more of an RSSI, an SINR, anMCS, and an NSS. The metric may be normalized to indicate relativechannel information between the measured sub-bands.

In an embodiment, computing an RSSI, an SINR, or both of a sub-band mayinclude computing an average of RSSIs or SINRs, respectively, of thesubcarriers that belong to the sub-band. In an embodiment, computing anMCS of a sub-band may include computing a highest bit rate MCS thatmeets a Packet Error Rate (PER) requirement. In an embodiment, computingan NSS of a sub-band may include computing a highest NSS that meets thePER requirement.

At S710, the station determines how to select which OFDMA sub-band CSIto report. Selecting the OFDMA sub-band CSI to be reported may includeone or more of combining and omitting information associated with themeasured sub-bands. For example, the STA may report the measured valuesfor sub-bands that meet a criterion (such as a channel strength, RSSI orSINR being larger than a threshold or an MCS having a larger index valueor data rate than a given reference MCS) and omit reporting the measuredvalues for the sub-bands that do not meet the criterion.

Because sub-bands that are not selected for reporting did not satisfythe criteria, an AP receiving the selected CSI may determine that theone or more sub-bands for which CSI was not reported are unsuitable ordisfavored for use in communicating with the station providing thereport. Accordingly, selective reporting of the CSI produces feedbackthat is more concise than feedback that reports all the CSI while stillreporting the most useful feedback, that is, the feedback on sub-bandsthat are suitable for consideration during selection of sub-bands forcommunicating with the station.

When an indication of which OFDMA sub-band CSI to report has beenreceived from the AP, at S716 the station determines the OFDMA sub-bandCSI to report using indications from the AP and the determined channelsstrengths. In an embodiment, the station may determine the OFDMAsub-band CSI to be reported according to parameters, a policy, or bothreceived in a NDPA, Action, or Action No ACK frame.

When the AP has not indicated the OFDMA sub-band CSI to be reported, atS714 the station determines the OFDMA sub-band CSI to report accordingto a station policy and the determined channels strengths.

Determining the OFDMA sub-band CSI to be reported may include combiningmeasurements. The measurements to be combined or averaged may bemeasurements from adjacent sub-bands, measurements associated withdifferent antennas, or both.

In an embodiment, measurements for a plurality of adjacent sub-bands arecombined into a single measurement when a measurement bandwidthresolution is greater than or equal to the combined bandwidths of theplurality of adjacent sub-bands. In an embodiment, the station maydetermine to combine measurements for a plurality of adjacent sub-bandswhen a difference or a ratio between one or more respective measurementsof the adjacent sub-bands is less than one or more respectivepredetermined thresholds.

In an embodiment, measurements for a plurality of transmitting antennas,receiving antennas, or combinations of receiving and transmittingantennas may be combined into a single measurement. In an embodiment,the station may determine to combine measurements for a plurality ofantennas when a difference or a ratio between one or more respectivemeasurements of the antennas is less than one or more respectivepredetermined thresholds.

Determining the OFDMA sub-band CSI to be reported may includedetermining which sub-bands to report on. In an embodiment, thesub-bands to be reported may be determined according to an indication ofwhich sub-bands to report on included in the NDPA frame sent by the AP.The NDPA frame may include on or more identifiers to identify the STAsto report, such as one or more of an identification associated with astation, a group identification, and a broadcast identification.

In an embodiment, the sub-bands to be reported may be determined by thestation according to a reporting policy of the station. The reportingpolicy may control which sub-band CSI is reported according to prior CSIreported for each sub-band, according to a suitability evaluation foreach sub-band, or both.

In an embodiment, the station may only report a sub-band when thecurrent CSI of the sub-band is substantially different from previouslyreported CSI for the sub-band.

In an embodiment, the current CSI of the sub-band may be substantiallydifferent from the previously reported CSI for the sub-band when, forexample, one or more of a current RSSI, SINR, MCS, NSS, and relativechannel strength differ from a respective one or more previouslyreported RSSI, SINR, MCS, NSS, and channel strength measure by arespective predetermined value.

In an embodiment, the current CSI of the sub-band may be substantiallydifferent from the previously reported CSI for the sub-band when, forexample, a ratio of one or more of a current RSSI, SINR, MCS, NSS, andchannel strength measure to a respective one or more previously reportedRSSI, SINR, MCS, NSS, and channel strength measure is greater than orless than a respective predetermined value.

In an embodiment, the sub-bands to be reported may be determined by thestation according to the suitability of each sub-band for transmittingframes to the station. In an embodiment, the CSI of a sub-band isreported only when one or more of the RSSI, SINR, MCS, NSS, and channelstrength measure meets a respective criteria. For example, a CSI of asub-band may only be reported when the SINR exceeds a predeterminedvalue, the MCS is one of a plurality of preferred modulation and codingschemes, the relative signal strength is within a predetermined toppercentile of the relative signal strengths of the measured sub-bands,or a combination of these criteria.

At S720, the station determines whether the OFDMA sub-band CSI is to besent unsolicited, i.e., without a targeted instruction from the AP tothe station. In an embodiment, the OFDMA sub-band CSI is sentunsolicited when the downlink frame used to perform the channelmeasurements is an NDP frame and the station is the first or onlystation indicated as performing channel measurements using the downlinkframe.

When the OFDMA sub-band CSI is not to be sent unsolicited, at S722 thestation waits for a poll frame to be received. The poll frame may pollseveral stations among which are the station. For example, the pollframe may be a Trigger frame that polls several STAs to send frames inUL OFDMA or UL MU-MIMO formats.

When the OFDMA sub-band CSI is to be sent unsolicited or after a pollframe is received, at S724 the station transmits the OFDMA sub-band CSI.In an embodiment, the station transmits the OFDMA in a management frameof type Action or Action No ACK, the management frame having an Actionfield with a value indicating that OFDMA sub-band CSI is being reported.

In an embodiment, the station transmits the OFDMA sub-band CSI to bereported in an uplink frame having an HT Control field including a HighEfficiency Control Extension field including the reported OFDMA sub-bandCSI and an indication that OFDMA sub-band CSI is being reported.

FIG. 8 illustrates an AP initiated sub-band sounding process 800 forOFDMA downlink operations according to another embodiment. In theillustrated example, a BSS includes an AP and first, second, and thirdOFDMA-capable stations STA1, STA2, and STA3.

At S802, the AP transmits a Null Data Packet Announcement (NDPA) frameto the stations STA1, STA2, and STA3, e.g., to all the stationsassociated with the BSS. The NDPA frame is transmitted at a widestallowable bandwidth, wherein the widest allowable bandwidth is thewidest bandwidth that can be transmitted across its entirety by the AP,received across its entirety by the stations in the BSS, and sensedacross its entirety by active channel sensing (e.g., Clear ChannelAssessment (CCA)).

The NDPA frame includes an indication that this process is for an OFDMAprocedure, an indication that the NDPA frame is applicable to a set ofOFDMA-capable stations, and an indication that the NDPA frame isapplicable to all stations associated with the BSS. The NDPA frameincludes an indication that a subsequent frame transmitted by the AP,for example, a Null Data Packet (NDP) frame, is to be used as a soundingframe by one or more of the stations STA1, STA2, and STA3 to determineOFDMA sub-band channel state information (CSI). The NDPA frame may alsoinclude an indication of whether each station is to provide solicited orunsolicited reporting of the OFDMA sub-band CSI.

To designate which stations are to determine the OFDMA sub-band CSI, theNDPA frame may include one or more addresses or identifiers respectivelycorresponding to stations in the BSS, an identifier of a previouslyestablished group of stations in the BSS, or an indication correspondingto all of the stations in the BSS.

In an embodiment, the NDPA frame may further include parameters for usein determining and reporting the OFDMA sub-band CSI. The parameters mayinclude one or more of a bandwidth resolution and an indication of oneor more sub-bands to be reported on or not reported on.

At S804, the AP transmits the sounding frame to be used for OFDMAsub-band sounding, which is an NDP frame in an implementation. The NDPframe is transmitted at the same widest allowable bandwidth as the NDPAframe was at S802. The stations STA1, STA2, and STA3 each determinesrespective OFDMA sub-band CSI using the NDP frame, e.g., RSSI, SINR,MCS, and NSS per sub-band for each of AP's transmitting antennas withrespect to each of station's receiving antennas. In an embodiment, thestations STA1, STA2, and STA3 determine the OFDMA sub-band CSI using LTFsymbols such as VHT-LTF or HE-LTF symbols of the NDP frame.

At S810, the first station STA1 transmits a first OFDMA sub-band CSIreport frame CSI1 to the AP. The first OFDMA sub-band CSI report frameCSI1 is a report transmitted in response to the NDP frame of S804, andincludes OFDMA sub-band CSI determined by the first station STA1according to the NDPA frame of S802 and the NDP frame of S804. In anembodiment, each station sends their respective CSI report frame eitherunsolicited or whenever the AP sends a request.

In an embodiment, the OFDMA sub-band CSI report frame CSI1 may be a MACframe including the OFDMA sub-band CSI in a High Efficiency ControlExtension (HECE) field of a High Throughput Control (HT Control) field.In an embodiment, the OFDMA sub-band CSI report frame CSI1 may be anAction or Action No ACK management frame, each of which would include anAction field indicating that the frame is an OFDMA sub-band CSI reportframe.

In an embodiment, the first station STA1 transmits the OFDMA sub-bandCSI report frame CSI1 unsolicited, that is, without receiving a triggeror request frame, and subsequent stations STA2 and STA3 transmitrespective OFDMA sub-band CSI report frames CSI2 and CSI3 in response toreceiving respective trigger or request frames.

At S812, the AP transmits a first OFDMA sub-band CSI poll frame CSIP1 tothe second station STA2. The first OFDMA sub-band CSI poll frame CSIP1may include indications such as the STA identifier, a reference to theidentification of an earlier NDPA frame, and a set of identifiers toreference the sub-bands that CSI is sent to the AP. In an embodiment,the first OFDMA sub-band CSI poll frame CSIP1 may include an indicationthat the frame is an OFDMA sub-band CSI poll frame.

At S820, in response to the first OFDMA sub-band CSI poll frame CSIP1,the second station STA2 transmits a second OFDMA sub-band CSI reportframe CSI2 to the AP. The second OFDMA sub-band CSI report frame CSI2 isa solicited report, and includes OFDMA sub-band CSI determined by thesecond station STA2 according to the NDPA frame of S802 and the NDPframe of S804.

At S822, the AP transmits a second OFDMA sub-band CSI poll frame CSIP2to the third station STA3. The second OFDMA sub-band CSI poll frameCSIP2 may include indications such as the STA identifier, a reference tothe identification of an earlier NDPA frame, and a set of identifiers toreference the sub-bands that CSI is sent to the AP. In an embodiment,the second OFDMA sub-band CSI poll frame CSIP2 may include an indicationthat the frame is an OFDMA sub-band CSI poll frame.

At S830, in response to the second OFDMA sub-band CSI poll frame CSIP2,the third station STA3 transmits a third OFDMA sub-band CSI report frameCSI3 to the AP. The third OFDMA sub-band CSI report frame CSI3 is asolicited report, and includes OFDMA sub-band CSI determined by thethird station STA3 according to the NDPA frame of S802 and the NDP frameof S804.

The AP determines an allocation of sub-bands to stations in the BSSaccording to the information included in the first, second, and thirdOFDMA sub-band CSI report frames CSI1, CSI2, and CSI3.

FIG. 9 illustrates a Null Data Packet Announcement (NDPA) frame 900according to an embodiment. The NDPA frame 900 is an OFDM MAC frame thatis a modification of the Very High Throughput (VHT) NDPA frame describedin § 8.3.1.20 of IEEE Std 802.11ac. In the interest of brevity, when aframe is a modification of an IEEE Std 802.11 frame, primarilydifferences between the variant frame and the standard frame will bedescribed, but other differences between the two frame types may exist.

In the NDPA frame 900, a bit in the Sounding Dialog Token 910 that was areserved bit in the VHT NDPA frame is used as an OFDMA Sub-bandReporting field 914. When the OFDMA Sub-band Reporting field 914 has afirst value, for example, a value of 1, the NDPA frame 900 indicatesthat one or more stations are to perform OFDMA sub-band CSIdetermination instead of performing VHT CSI determination. When theOFDMA Sub-band Reporting field 914 has a second value, for example, avalue of 0, the NDPA frame 900 does not indicate that OFDMA sub-band CSIdetermination is to be performed, and in an embodiment may insteadindicate that VHT CSI determination is to be performed.

The Sounding Dialog Token 910 further includes a Sounding Dialog TokenNumber field 916 that identifies the NDPA frame 900 and may be used toassociate a sounding request with corresponding responses.

The NDPA frame 900 may include one or more station (STA) info fields 920that indicate which stations are to perform OFDMA sub-band CSIdetermination. The stations may be indicated by the AssociationIdentifier subset (AID12) fields 922 of the STA info fields 920, whichinclude the 12 least significant bits of the AID of a station expectedto process the following NDP frame and prepare the sounding feedback.The STA info fields 920 may also supply parameters to be used by thecorresponding stations in the OFDMA sub-band CSI determination, usingone or more of the Feedback Type field 924 and the Nc Index field 926.

In an embodiment, when the NDPA frame 900 indicates that OFDMA sub-bandCSI determination is to be performed, all stations indicated in the NDPAframe perform the OFDMA sub-band CSI determination.

FIG. 10 illustrates an NDPA frame 1000 according to another embodiment.The NDPA frame 1000 is another modification of the VHT NDPA framedescribed in § 8.3.1.20 of IEEE Std 802.11ac.

In the NDPA frame 1000, a Sounding Dialog Token Number (SDTN) field 1016of the Sounding Dialog Token field 1010 having a predetermined value,such as all 0's or all 1's, indicates that one or more stations are toperform OFDMA sub-band CSI determination instead of performing VHT CSIdetermination. When the SDTN field 1016 does not have the predeterminedvalue, the NDPA frame 900 does not indicate that OFDMA sub-band CSIdetermination is to be performed, and may instead indicate that VHT CSIdetermination is to be performed according to an embodiment.

The NDPA frame 1000 may include one or more STA info fields 1020 thatindicate which stations are to perform OFDMA sub-band CSI determination,and may communicate parameters to be used in performing the OFDMAsub-band CSI determination, as described above for the STA info fields920 of FIG. 9.

FIG. 11 illustrates NDPA frame 1100 according to another embodiment,wherein the NDPA frame 1100 may indicate that all stations in the BSSare to perform OFDMA sub-band CSI determination. The NDPA frame 1100 isa modification of the NDPA frame 900 of FIG. 9.

The NDPA frame 1100 uses bits in the Sounding Dialog field 1110 as anOFDMA Sub-band Reporting sub-field 1114 and a Broadcast OFDMA NDPAsub-field 1112. The OFDMA Sub-band Reporting field 1114 operates asdescribed for the OFDMA Sub-band Reporting field 914 of FIG. 9. TheSounding Dialog field 1110 further includes a Sounding Dialog TokenNumber sub-field 1116 that operates as described for the Sounding DialogToken Number field 916 of FIG. 9.

When the OFDMA Sub-band Reporting field 1114 indicates that OFDMAsub-band CSI determination is to be performed, the Broadcast OFDMA NDPAfield 1112 having a first value, for example, a value of 1, indicatesthat all of the stations in the BSS are to perform the OFDMA sub-bandCSI determination. In an embodiment, the NDPA frame 1100 may have no STAinfo fields when the Broadcast OFDMA NDPA field 1112 indicates that allof the associated stations in the BSS, or all of the associated stationsin the BSS that are OFDMA-capable, are to perform the OFDMA sub-band CSIdetermination.

FIG. 12 illustrates an NDPA frame 1200 according to another embodiment,wherein the NDPA frame 1200 may indicate that all stations in the BSSare to perform OFDMA sub-band CSI determination. The NDPA frame 1200 isa modification of the NDPA frame 900 of FIG. 9.

When a Sounding Dialog Token 1210 of the NDPA frame 1200 indicates thatOFDMA sub-band CSI determination is to be performed, an AssociationIdentifier subset (AID12) field of a STA info field 1220 of the NDPAframe 1200 having a predetermined value, such as all zeros, indicatesthat all of the associated stations in the BSS, or all of the associatedstations on the BSS that are OFDMA-capable are to perform the OFDMAsub-band CSI determination.

FIG. 13 illustrates an OFDMA CSI Request frame 1300 for requesting OFDMAsub-band channels state information (CSI) according to anotherembodiment. The OFDMA CSI Request frame 1300 is based on the format ofthe Beamforming (BF) Report Poll frame described in § 8.3.1.21 of IEEEStd 802.11ac™-2013. The OFDMA CSI Request frame 1300 differs from the BFReport Poll frame in having a different value in the Frame Control field1304 and a Sounding Dialog field 1310 instead of a Feedback SegmentRetransmission Bitmap field.

The Sounding Dialog field 1310 includes a Broadcast OFDMA NDPA sub-field1312, an OFDMA Sub-band Reporting sub-field 1314, and a Sounding DialogToken Number sub-field 1316 that respectively operate as described forthe Broadcast OFDMA NDPA sub-field 1112, OFDMA Sub-band Reportingsub-field 1114, and a Sounding Dialog Token Number sub-field 1116 shownin FIG. 11.

In an embodiment, the frame body 1320 also includes one or more STA infofields, each similar to the STA info field 920 of FIG. 9.

FIG. 14 illustrates a Media Access Control (MAC) frame 1400 includingHigh Efficiency (HE) fields according to an embodiment, which may beused to report the results of an OFDMA sub-band CSI determination. TheMAC frame 1400 is a modification of a MAC frame described in § 8.2 ofIEEE Std 802.11ac, and includes a High Throughput (HT) Control field1430 and an HT Control Middle field 1450 that are modifications of a VHTvariant HT Control field and a VHT variant HT Control Middle fielddescribed in §§ 8.2.4.6 through 8.2.4.6.3 of that standard,respectively.

A bit in the HT Control middle field 1450 of the MAC frame 1400, denotedas an HE Control Extension Indication field 1452, is used to indicatethe extension of HTC field and addition of HE Control Extension. Whenthe HE Control Extension Indication field 1452 has a first value, forexample, a value of “1”, the HT Control field 1430 includes an HEControl Extension (HECE) field 1432.

The HECE field 1432 may include OFDMA sub-band CSI including one or moreof the information shown in Table 1, below. The information shown inTable 1 may be included in the HECE field 1432 for each of selectedsub-band, each of a plurality of adjacent of sub-bands, each of aplurality of combinations of a sub-band and a plurality of receivingantennas, transmitting antennas, or both, and the like.

TABLE 1 HECE Information ULDL Indicates whether the report is fordownlink (DL) OFDMA or uplink (UL) OFDMA. BW Bandwidth of the frequencysegment for which OFDMA sub-band CSI was determined NDPA SDTN SoundingDialog Token Number from the NDPA or other frame that requested theOFDMA sub-band CSI. Sub-band resolution Bandwidth covered by eachreported CSI. MCS per sub-band Modulation and Coding Scheme for eachsub-band NSS per sub-band Number of special streams for each sub-bandQueue Size per AC Queue size per Access Category Queue Size per TIDQueue size per Traffic Identifier

FIG. 15 illustrates an OFDMA CSI Report frame 1500 for reporting OFDMAsub-band CSI according to another embodiment. The OFDMA CSI Report frame1500 is a management frame in the format Action frame or an Action NoACK frame as described in § 8.3.3.13 or § 8.3.3.14, respectively, ofIEEE Std 802.11-2012. In addition to the fields shown, the OFDMA CSIReport frame 1500 may include a QoS Control field.

A frame body 1520 of the OFDMA CSI Report frame 1500 includes anCategory field 1512 and an HE Action field 1516 indicating that theframe is an OFDMA Subband CSI Report. The frame body 1520 furtherincludes a Report Information field 1514 including one or more of theinformation shown in Table 1, above. The information shown in Table 1may be included in the Report Information field 1514 for each ofselected sub-bands, each of a plurality of adjacent sub-bands, each of aplurality of combinations of a sub-band and a plurality of receivingantennas, transmitting antennas, or both, and the like.

The Report Information field 1514 include two fields: (1) a ReportControl field 1522, and (2) a Report field 1524 that has Report Valuefor all sub-bands.

The Report Control field 1522 may include, among others, the followingsub-fields: Sub-band Report BW (2 MHz, 4 MHz, 8 MHz, 10 MHz, 20 MHz, 40MHz, 80 MHz, or 80+80/160 MHz), Report Type (SINR, MCS, NSS, RSSI), andDLUL Report (DL Report, UL Report, i.e. whether the Report field is DLReport or UL Report). In an embodiment, the Report Control field 1522also includes a Report Value Length indication a length of the ReportField 1524.

The Report field includes the Report Value for each sub-band. In anembodiment, a length of the Report Value may be predetermined. Inanother embodiment, the length of the Report Value is indicated in thecorresponding Report Control field. Given the Sub-band Report BW, thenumber of Report Values are a priori known.

There might be more than one Report Information field 1514, whichresults in having more than one pair of Report Control field 1522 andReport field 1524. For instance, there might be one Report Control field1522 and Report field 1524 for MCS and another Report Control field 1522and Report field 1524 for NSS, and/or another Report Control field 1522and Report field 1524 for SINR. In another embodiment, a Report Valuemight have combined reports e.g. MCS and NSS all within one Report Valuesub-field but with a known bit boundaries such that the recipient of thereport would distinguish and extract MCS and NSS reports separately. Insuch multiple report cases, there would be a designated indicationwithin Report Type. For instance the Report Type would indicate (SINR,MCS, NSS, MCS+NSS, SINR+MCS, RSSI+NSS, and other possible combinations).

In some embodiments, the Report field 1524 includes an extra sub-field,named Queue Size, to indicate the queue size of all or each AccessCategory (AC) at the STA side. The Report Control field 1514 includes anindicator to indicate the presence of the queue size sub-field, whereinthe indicator being set to a TRUE value indicates the presence of QueueSize sub-field within the Report field, otherwise the indicator beingset to FALSE value indicates that the Queue Size sub-field is notpresent. If the STA does not want to report any queue size a reservedvalue is used, such as setting the sub-field to all-zero or all-one.

The Queue Size sub-field has a length of 1 or 2 octet(s) and indicatesthe total queue size of all ACs, in units of a pre-determined number ofBytes, or it might have four sub-fields each indicating the queue sizeof respective ACs in units of a pre-determined number of Bytes.

In some embodiments, the OFDMA CSI Report frame 1500 might appear in twoforms: an OFDMA CSI Report Request and an OFDMA CSI Report Response. Inthe OFDMA CSI Report Request, only the Report Control field is presentand the Report field is not present, while in the OFDMA CSI ReportResponse both of the fields are present. In some embodiments, the OFDMACSI Report Request and the OFDMA CSI Report Response are distinguishedby a sub-field in the Report Control field, where this sub-field isdenoted by Request/Response that indicates that the frame is the OFDMACSI Report Request when it is set to a REQUEST value and indicates thatthe frame is the OFDMA CSI Report Response when it is set to a RESPONSEvalue.

FIG. 16 illustrates an AP-initiated channel sounding process 1600according to another embodiment. In the illustrated example, a BSSincludes an AP and first, second, and third OFDMA-capable stations STA1,STA2, and STA3. In the process 1600, an OFDM transmitted for anotherpurpose, such as, for example, a MAC data frame, a MAC control frame, ora MAC management frame, is also used for OFDMA sub-band sounding.

At S1602, the AP transmits a Null Data Packet Announcement (NDPA) frameto all of stations STA1, STA2, and STA3. The NDPA frame is transmittedat a widest allowable bandwidth, wherein the widest allowable bandwidthis the widest bandwidth that can be transmitted by the AP, received bythe stations in the BSS, and sensed by active channel sensing used, forexample, for Clear Channel Assessment (CCA).

The NDPA frame includes an indication that a subsequent OFDM downlinkframe transmitted by the AP, such as an OFDM NDP frame or a control ordata frame with one or multiple LTF symbols, is to be used by one ormore of the stations STA1, STA2, and STA3 as a sounding frame todetermine OFDMA sub-band CSI. The NDPA frame may also include anindication of whether each station is to provide solicited orunsolicited reporting of the OFDMA sub-band CSI.

To designate which stations are to determine the OFDMA sub-band CSI, theNDPA frame may include one or more addresses or identifiers respectivelycorresponding to stations in the BSS, an identifier of a previouslyestablished group of stations in the BSS, or an indication correspondingto all of the stations in the BSS.

In an embodiment, the NDPA frame may further include parameters for usein determining and reporting the OFDMA sub-band CSI. The parameters mayinclude one or more of a bandwidth resolution and an indication of oneor more sub-bands to be reported on or not reported on.

At S1612, the AP transmits the OFDM downlink (OFDM_DF) frame to be usedas the sounding frame for OFDMA sub-band sounding. The OFDM_DF frame maybe an OFDM NDP frame or a control or data frame with one or multiple LTFsymbols, for example, a MAC data frame, a MAC control frame, or a MACmanagement frame transmitted for another purpose as well as for OFDMAsub-band sounding. The OFDM_DF frame is transmitted at the same widestallowable bandwidth as the NDPA frame was at S1602.

The stations STA1, STA2, and STA3 each determine respective OFDMAsub-band CSI using the OFDM_DF frame. In an embodiment, the stationsSTA1, STA2, and STA3 determine the OFDMA sub-band CSI using an LTFsymbol such as VHT-LTF or HE-LTF symbol of the OFDM_DF frame.

In some embodiments, the OFDM_DF frame includes a Sounding_Allowedindicator in its HE SIG-A or HE SIG-B symbol. The Sounding_Allowedindicator indicates whether channel sounding based on HE LTF symbols isallowed. When the LTF symbols are beamformed to a specific STA, theOFDMA sounding procedure performed by other STAs based on the beamformedLTF symbols would not be accurate and in this case the AP shall set theSounding_Allowed indicator to a FALSE value. In some embodiments, theOFDM_DF frame may be in an OFDMA format with the Sounding_Allowedindicator set to a TRUE value and HE LTF symbols are not beamformed.

In an embodiment, the LTF symbols of a Trigger frame (a HE frame that issent to a set of stations to trigger simultaneous transmission of aresponse frame by the set of stations or by a subset of the stations) isused to perform OFDMA sounding procedure. In such case, the Triggerframe may be sent in an OFDMA format to a set of stations, and may be abroadcast frame to all the associated stations, and the Sounding_Allowedindicator is set to allow the recipient stations to perform sounding.

Some of the stations, which are addressed in the Trigger frame, may sendan OFDMA CSI Report frame 1500 as part of an immediate response to theTrigger frame (i.e. the OFDMA CSI Report frame is either sent as an MPDUin an A-MPDU of possibly other control, management or data frames, or aOFDMA CSI Report frame might be sent as a single MDPU). This means thatthe responding stations send the OFDMA CSR Report frame, possibly alongwith other (data, management or control) frames, in an UL OFDMA or ULMU-MIMO frame (where each station uses the sub-band or resource unitsassigned to the station as announced in the preceding Trigger frame).

Some other stations might later send an OFDMA CSI Report frame 1500 as aseparate management frame or as an MPDU within an A-MPDU. In oneembodiment, a special Trigger frame might be used to seek OFDMA CSIReport frames from the identified stations (or a set of stationsidentified by a group-identification). In another embodiment, inaddition to an OFDMA CSI Report frame a station might provide its queuesize per Access Category (AC) or per all ACs within a QoS Control fieldor within the Queue Size sub-field of the OFDMA CSI Report frame.

At S1620, the AP transmits a first OFDMA sub-band CSI poll frame CSIP1,to the first station STA1. In an embodiment, the first OFDMA sub-bandCSI poll frame CSIP1 is instead an OFDMA sub-band CSI Request frame.

At S1622, in response to the first OFDMA sub-band CSI poll frame CSIP1,the first station STA1 transmits a first OFDMA sub-band CSI report frameCSI1 to the AP. The first OFDMA sub-band CSI report frame CSI2 is asolicited report, and includes OFDMA sub-band CSI determined by thefirst station STA1 according to the NDPA frame of S1602 and the OFDM_DFframe of S1612.

At S1624, the AP transmits a second OFDMA sub-band CSI poll frame CSIP2to the second station STA2. In an embodiment, the second OFDMA sub-bandCSI poll frame CSIP2 is instead an OFDMA sub-band CSI Request frame.

At S1626, in response to the second OFDMA sub-band CSI poll frame CSIP2,the second station STA2 transmits a second OFDMA sub-band CSI reportframe CSI2 to the AP. The second OFDMA sub-band CSI report frame CSI2 isa solicited report, and includes OFDMA sub-band CSI determined by thesecond station STA2 according to the NDPA frame of S1602 and the OFDM_DFframe of S1612.

At S1628, the AP transmits a third OFDMA sub-band CSI poll frame CSIP3to the third station STA3. In an embodiment, the third OFDMA sub-bandCSI poll frame CSIP2 is instead an OFDMA sub-band CSI Request frame.

At S1630, in response to the third OFDMA sub-band CSI poll frame CSIP3,the third station STA3 transmits a third OFDMA sub-band CSI report frameCSI3 to the AP. The third OFDMA sub-band CSI report frame CSI3 is asolicited report, and includes OFDMA sub-band CSI determined by thesecond station STA2 according to the NDPA frame of S1602 and the OFDM_DFframe of S1612.

In an embodiment, OFDMA sub-band CSI report frames may be MAC framesincluding OFDMA sub-band CSI in a High Efficiency Control Extension(HECE) field of a High Throughput Control (HT Control) field. In anembodiment, OFDMA sub-band CSI report frames may be an Action or ActionNo ACK frames including an Action field indicating that the frame is anOFDMA sub-band CSI report frame.

In some embodiments, the sequence of NDPA frame and OFDM_DF frame inFIG. 16 can be replaced by a single frame such as a single Triggerframe. A Trigger frame has the role of polling several stations toparticipate in an Up Link Multi-User (UL MU) transmission, such as ULOFDMA. The stations participate in the UL MU by sending data frames orspecific control or management frames in an UL MU PPDU format (i.e. ULOFDMA or UL MU-MIMO format).

In such embodiments, the AP indicates a set of STAs in a Trigger frameby indicating the RA or other IDs of the STAs along with otherinformation such as the sub-band that each STA would use in the upcomingUL OFDMA frame.

The AP sends the Trigger frame in an OFDM format. The Trigger frame mayinclude multiple HE LTF symbols (where an indicator in an HE SIG-A or HESIG-B symbol of the Trigger frame indicates the number of HE LTF symbolspresent in the frame). The AP may set a Sounding_Allowed indicator ofthe Trigger frame to a TRUE value to direct the indicated STAs toperform sounding based on the HE LTF symbols within the Trigger frame.

The indicated STAs would then participate in the UL OFDMA or UL MU MIMOframe and send the OFDMA sub-band CSI report either in a High EfficiencyControl Extension (HECE) field of a High Throughput Control (HT Control)field of the MAC header of the frame they send to the AP (such as shownin FIG. 14), or as a management frame such as the OFDMA CSI Report frameshown in FIG. 15. In some embodiments, some of the indicated stationswould include Queue Size sub-field within OFDMA CSI Report. In someembodiments, the indicated stations respond with data, control, ormanagement frames within an A-MPDU where one of the MPDUs is the OFDMACSI Report.

The AP determines an allocation of sub-bands to stations participatingin the MU transmission according to the information included in thefirst, second, and third OFDMA sub-band CSI report frames CSI1, CSI2,and CSI3.

FIG. 17 illustrates a process 1700 of determining OFDMA sub-band CSI ina station according to an embodiment.

At S1702, the station receives an indication that OFDMA sub-band CSI isto be determined. The indication may be received in an NDPA frame, anAction frame or an Action No ACK frame addressed to the station,addressed to a group the station is included in, or addressed to all thestations in the BSS. The NDPA, Action, or Action No ACK frame includingthe indication at OFDMA sub-band CSI is to be determined may betransmitted by an AP.

At S1704, the station measures one or more characteristics of a channelbetween a transmitter of a downlink frame, such as the AP, and thestation. The station measures the channel characteristics using one ormore fields of the downlink frame, such as, for example, an LTF symbol,e.g., VHT-LTF or HE-LTF symbols.

In an embodiment, the downlink frame may be a NDP transmitted using afrequency segment having a widest allowable bandwidth. In an embodiment,the downlink frame may be a MAC Control frame, a MAC Data frame, or aMAC Management frame transmitted using the frequency segment having thewidest allowable bandwidth. The widest allowable bandwidth is a widestbandwidth that can be transmitted across its entirety by thetransmitter, received across its entirety by the stations in the BSS,and sensed across its entirety by active channel sensing.

In an embodiment, the station may measure only some of the sub-bandswithin the frequency segment. The sub-bands to be measured may bedetermined using an indication in the received NDPA, Action, or ActionNo ACK frame that included the indication that OFDMA sub-band CSI was tobe determined. In an embodiment, the received indication of whichsub-bands to measure may include an indication determined according to aprior allocation of one or more sub-bands to one or more other stations.In an embodiment, the received indication of which sub-bands to measuremay be determined according to prior OFDMA sub-band CSI provided by thestation.

The measurements taken for each sub-band may include a Received SignalStrength Indication (RSSI), a Signal to Interference and Noise Ratio(SINR), an estimated best Modulation and Coding Scheme (MCS), and aNumber of Spatial Streams (NSS). In an embodiment, measurements for eachof a plurality of subcarriers of each sub-band are combined to determinea respective measurement for each sub-band.

The measurements for each sub-band may be taken for each of a pluralityof transmitting antennas when the downlink frame is transmitted usingthe plurality of transmitting antennas. The measurements for eachsub-band may be taken for each of a plurality of receiving antennas whenthe downlink frame is received using the plurality of receivingantennas.

At S1706, the station determines the channel strength measures for eachmeasured sub-band. In an embodiment, the channel strength measures foreach measured sub-band are determined for each transmitting antenna, foreach receiving antenna, or for each combination of a transmittingantenna and a receiving antenna.

Determining the channel strength measures for each measured sub-band mayinclude computing a metric using one or more of an RSSI, an SINR, anMCS, and an NSS. The metric may be normalized to indicate relativechannel information between the measured sub-bands.

At S1710, the station determines the OFDMA sub-band CSI to be reported.Determining the OFDMA sub-band CSI to be reported may include one ormore of combining and omitting information associated with the measuredsub-band.

In an embodiment, the station may determine the OFDMA sub-band CSI to bereported according to a policy received in the received NDPA, Action, orAction No ACK frame that included the indication that OFDMA sub-band CSIwas to be determined. In an embodiment, the station may determine thesub-band CSI to be reported according to an internal policy of thestation.

Determining the OFDMA sub-band CSI to be reported may include combiningmeasurements. The measurements to be combined may be measurements fromadjacent sub-bands, measurements associated with different antennas, orboth.

In an embodiment, measurements for a plurality of adjacent sub-bands arecombined into a single measurement when a measurement bandwidthresolution or the requested resolution for the measurement is greaterthan the combine bandwidths of the plurality of adjacent sub-bands. Inan embodiment, the station may determine to combine measurements for aplurality of adjacent sub-bands when a difference or a ratio between oneor more respective measurements of the adjacent sub-bands is less thanone or more respective predetermined thresholds.

In an embodiment, measurements for a plurality of transmitting antennas,receiving antennas, or both, may be combined into a single measurement.In an embodiment, the station may determine to combine measurements fora plurality of transmitting antennas when a difference or a ratiobetween one or more respective measurements of the antennas is less thanone or more respective predetermined thresholds.

Determining the OFDMA sub-band CSI to be reported may includedetermining which sub-bands to report on. In an embodiment, thesub-bands to be reported may be determined according to an indication ofwhich sub-bands to report on included in the NDPA, Action, or Action NoACK frame that included the indication that OFDMA sub-band CSI was to bedetermined.

In an embodiment, the sub-bands to be reported may be determined by thestation according to a reporting policy of the station. The reportingpolicy may control which sub-band CSI is reported according to prior CSIreported for each sub-band, according to a suitability evaluation foreach sub-band, or both.

In an embodiment, the station may only report a sub-band when thecurrent CSI of the sub-band is substantially different from previouslyreported CSI for the sub-band.

In an embodiment, the current CSI of the sub-band may be substantiallydifferent from the previously reported CSI for the sub-band when, forexample, one or more of a current RSSI, SINR, MCS, NSS, and channelstrength measure differ from a respective one or more previouslyreported RSSI, SINR, MCS, NSS, and channel strength measure by arespective predetermined value.

In an embodiment, the current CSI of the sub-band may be substantiallydifferent from the previously reported CSI for the sub-band when, forexample, a ratio of one or more of a current RSSI, SINR, MCS, NSS, andchannel strength measure to a respective one or more previously reportedRSSI, SINR, MCS, NSS, and channel strength measure is greater than orless than a respective predetermined value.

In an embodiment, the sub-bands to be reported may be determined by thestation according to the suitability of each sub-band for transmittingframes to the station. In an embodiment, the CSI of a sub-band isreported only when one or more of the RSS, SINR, MCS, NSS, and channelstrength measure meets a respective criteria. For example, a CSI of asub-band may only be reported when the SINR exceeds a predeterminedvalue, the MCS is one of a plurality of preferred modulation and codingschemes, the relative signal strength is within a predetermined toppercentile of the relative signal strengths of the measured sub-bands,or a combination of these criteria.

At S1720, the station determines whether the OFDMA sub-band CSI is to besent unsolicited, i.e., without a targeted instruction from the AP tothe station. In an embodiment, the OFDMA sub-band CSI is sentunsolicited when the downlink frame used to perform the channelmeasurements is an NDP frame and the station is the first or onlystation indicated as performing channel measurements using the downlinkframe.

In an embodiment, the frame used to perform channel measurement includesan indication whether the OFDMA sub-band CSI is to be sent unsolicited(that is, as a response to the frame used to perform channelmeasurement) or as a response to a subsequent poll frame. In anotherembodiment, an announcement frame used to pre-announce the frame used toperform channel measurement includes the indication whether the OFDMAsub-band CSI is to be sent as a response to the frame used to performchannel measurement or as a response to a subsequent poll frame.

When the OFDMA sub-band CSI is not to be sent unsolicited, at S1722 thestation waits for a poll frame to be received.

When the OFDMA sub-band CSI is to be sent unsolicited or after a pollframe is received, at S1724 the station transmits the OFDMA sub-bandCSI. In an embodiment, the station transmits the OFDMA in an Action orAction No ACK frame having an Action field with a value indicating thatOFDMA sub-band CSI is being reported.

In an embodiment, the station transmits the OFDMA sub-band CSI to bereported in an uplink frame having an HT Control field including a HighEfficiency Control Extension field including the reported OFDMA sub-bandCSI and an indication that OFDMA sub-band CSI is being reported.

At S1730 the station uses the OFDMA sub-band CSI to determine an MCS, anNSS, or both for a subsequent uplink (UL) transmission.

In another set of embodiments that are shown in FIG. 18A and FIG. 18B,one or more DL data frames are sent by the AP to a station STA andsubsequently the AP receives ACK or BA responses from the station STAregarding the previously sent DL data frames. The DL data frames mayinclude an OFDM frame or a multi-user frame, such as an OFDMA frame,where the AP expects to receive ACK/BA frames from the intendedstations, including the station STA, addressed in the previously sentmultiuser or OFDMA frame.

In a process disclosed herein, the station STA may send the ACK or BAframes using specific formats that may be used by the AP to determineinformation than can be used to enhance subsequent DL or UL OFDMA framesscheduled by the AP for a group of stations including the station STA.

If the AP and station STA are engaged in Single User (SU) transmissionthen this new process happens between the AP and the station STA. The APtransmits a Block Ack Request (BAR) frame in a specific format describedherein. The station STA responds with an ACK or BA frame in a specificformat that mirrors, that is, is transmitted in the same bandwidth as,the initial BAR frame.

In another embodiment, wherein the AP does not transmit a BAR frame, thestation STA responds with ACK or BA in a specific format that mirrorsthat is, is transmitted in the same bandwidth as, the preceding DLframe.

If the AP and several stations are engaged in a DL MU transmission (suchas an 802.11ac DL MU MIMO transmission or an 802.11ax DL OFDMAtransmission) then this new process happens between the AP, which sendsa BAR frame for each station in a specific format described here, andeach of the stations that responds with an ACK or BA frame in a specificformat that mirrors the initial BAR frame.

FIGS. 18A and 18B shows that the stations respond with ACK or BA framesin non-HT duplicated format such as that shown in FIG. 19, which isshown for 80 MHz bandwidth. The duplication structure of FIG. 19 can beapplied for non-HT duplicated formats with bandwidths of 40 MHz, 80 MHz,160 MHz or 80+80 MHz. However, embodiments are not limited to that shownin FIG. 19, and the stations may transmit ACK/BA frames in HT, VHT or HEformats with a bandwidth of 40 MHz, 80 MHz, 160 MHz or 80+80 MHz.

In an embodiment, when an AP transmits a BAR frame to a station STA topoll for a ACK/BA response from that station STA, the AP sends the BARframe in non-HT duplicated format (such that shown in FIG. 19). Theduplication structure of FIG. 19 can be applied for non-HT duplicatedformat with bandwidths of 40 MHz, 80 MHz, 160 MHz or 80+80 MHz.

FIG. 18A illustrates a station-initiated OFDMA sub-band sounding process1800 according to an embodiment. In the illustrated example, a BSSincludes an AP and first and second OFDMA-capable stations STA1 andSTA2.

At S1802, the first and second stations STA1 and STA2 receive a firstOFDM frame OFDM_DF1 from the AP. The first OFDM frame OFDM_DF1 mayinclude one or more of a MAC Control Frame, a MAC Data frame, or a MACManagement frame. In an embodiment, the first OFDM frame OFDM_DF1 is aBAR frame. The first OFDM frame OFDM_DF1 may be transmitted at a widestallowable bandwidth, as previously described.

In an embodiment, the first OFDM frame OFDM_DF1 may include anindication that OFDMA sub-band sounding is requested. In an embodiment,the first OFDM frame OFDM_DF1 is used as a sounding frame by the firstand second stations STA1 and STA2.

At S1804, the first station STA1 transmits a first ACK (or Block ACK)frame ACK/BA1 in response to the first OFDM frame OFDM_DF1. The firstACK frame ACK/BA1 is an OFDM frame.

Instead of transmitting the first ACK frame ACK/BA1 at a minimumrequired bandwidth, the first station STA1 transmits the first ACK frameACK/BA1 at the widest allowable bandwidth. When the widest allowablebandwidth is wider than a minimum bandwidth of a frequency segment, thefirst ACK frame ACK/BA1 may include information duplicated across thewidest allowable bandwidth, and the first ACK frame ACK/BA1 may includebandwidth indicators. The first ACK frame ACK/BA1 may include a non-HTduplicated frame.

The AP determines first OFDMA sub-band CSI for a first channel betweenthe AP and the first station STA1 using the first ACK frame ACK/BA1,e.g., by using one or more of an RSSI, a SINR, and MCS, and an NSS ofthe first ACK frame ACK/BA1.

At S1814, the second station STA2 transmits a second ACK (or Block ACK)frame ACK/BA2. The second ACK frame ACK/BA2 is an OFDM frame.

The second station STA2 transmits the second ACK frame ACK/BA2 at thewidest allowable bandwidth. When the widest allowable bandwidth is widerthan a minimum bandwidth of a frequency segment, the second ACK frameACK/BA2 may duplicate information across the widest allowable bandwidth,and the second ACK frame ACK/BA2 may include bandwidth indicators. Thesecond ACK frame ACK/BA2 may include a non-HT duplicated frame.

The AP determines second OFDMA sub-band CSI for a second channel betweenthe AP and the second station STA2 using the second ACK frame ACK/BA2,e.g., by using one or more of an RSSI, a SINR, and MCS, and an NSS ofthe second ACK frame ACK/BA2. The AP then allocates sub-bands to thestations in the BSS using the first and second OFDMA sub-band CSI.

In an embodiment, the second station STA2 transmits the second frameACK/BA2, e.g., according to carrier sense multiple access with collisionavoidance (CSMA/CA) protocol. For example, the second station STA2transmits the second frame ACK/BA2 in response to the first OFDM framereceived at S1802.

Alternatively, the second station STA2 may transmit the second frameACK/BA2 after receiving a second OFDM frame OFDM_DF2 from the AP atS1812′ (see FIG. 18B). The second OFDM frame OFDM_DF2 may include one ormore of a MAC Control Frame, a MAC Data frame, or a MAC Managementframe. The second OFDM frame OFDM_DF2 may be transmitted at the widestallowable bandwidth, as previously described. In an embodiment, thesecond OFDM frame OFDM_DF2 may include an indication that OFDMA sub-bandsounding is requested. In an embodiment, the second OFDM frame OFDM_DF2is used as a sounding frame by the second station STA2.

FIG. 19 illustrates a frame 1900 suitable for use in a station-initiatedOFDMA sub-band sounding process, such as the OFDMA sub-band soundingprocess 1800 of FIGS. 18A and 18B, according to an embodiment. The frame1900 is an OFDM uplink frame.

The frame 1900 is transmitted at a widest available bandwidth, which inthe embodiment of FIG. 19 is 80 MHz.

The frame 1900 includes a ACK/BA frame 1918 having a 20 MHz bandwidthand first, second, and third duplicate ACK/BA frames 1912, 1914, and1916 each occupying additional respective 20 MHz bandwidths. The first,second, and third duplicate ACK/BA frames 1912, 1914, and 1916 includeare identical in content to the ACK/BA frame 1918, and are used toduplicate the ACK/BA frame 1918 across the 80 MHz widest allowablebandwidth of the frame 1900.

In an embodiment, the frame 1900 may be in a legacy non-HT duplicatedformat. In an embodiment, the frame 1900 may be in a VHT or HE format,in which case no explicit duplication is needed.

FIG. 20 illustrates a station-initiated OFDMA sub-band sounding process2000 according to another embodiment.

At S2002, an AP transmits a beacon frame that is received by a stationSTA. The beacon frame may include an indication that the AP has apending downlink (DL) payload for the station STA.

In response to the beacon frame, at S2004 the station STA that has beenout of power-save (PS) mode transmits a response frame to the AP. Theframe may include an IEEE Std 802.11-2012 Power Save (PS)-Poll frame orQuality of Service (QoS) Null frame.

In the embodiments related to FIG. 20 and FIG. 21, the AP and STAsmodify a IEEE 802.11™-2012 PS-Poll frame and an associated IEEE802.11-2012 power management procedure to provide the AP with sub-bandinformation over the largest bandwidth that both AP and STA areconfigured to operate over and that the condition of the wireless mediumallows.

In the current procedures prescribed by the IEEE 802.11 specifications,a STA that has recently exited a power save mode sends a PS-Poll frameto the AP. The PS-Poll frame indicates to the AP that the STA is out ofsleep mode and ready to receive one or more DL payloads associated withthe STA. The AP acknowledges the reception of the PS-Poll frame andsubsequently sends the DL payloads to the STA. In some cases, the AP maysend the DL payload right after the reception of the PS-Poll frame.

In the modified PS-Poll procedure shown in FIG. 20 and FIG. 21, the STAssend PS-Poll frames in specific formats. The formats of the PS-Pollframes enable the AP to collects sub-carrier and/or sub-band informationfor the widest bandwidth possible.

The STA may send a PS-Poll frame in a non-HT duplicated format such thatshown in FIG. 21, which is shown for 80 MHz bandwidth. However,embodiments are not limited thereto, and the duplication structure ofFIG. 21 can be applied for non-HT duplicated formats with bandwidths of40 MHz, 80 MHz, 160 MHz, or 80+80 MHz. In another embodiment, thePS-Poll frame is sent in a HT, VHT or HE format with a bandwidth of 40MHz, 80 MHz, 160 MHz or 80+80 MHz.

The STA sends the PS-Poll frame in non-HT duplicate format with aCH_BANDWIDTH_IN_NON_HT parameter of the TXVECTOR set to indicate a 160MHz or 80+80 MHz bandwidth when both the AP and the STA operate with theindicated bandwidth and secondary20, secondary40 and secondary80channels are not sensed BUSY by the STA at a PIFS time beforetransmission of the frame.

In addition, when CH_BANDWIDTH_IN_NON_HT parameter of the TXVECTOR isset to larger than 20 MHz, the TA field value is the address of the STAtransmitting the frame or a bandwidth signaling TA. When the PS-Pollframe is transmitted by a VHT or HE STA in a non-HT or non-HT duplicateformat and a scrambling sequence of the PS-Poll frame carries theTXVECTOR parameter CH_BANDWIDTH_IN_NON_HT (such as the cases describedabove), the TA field value of the PS-Poll frame is a bandwidth signalingTA. When the ACK or BA frame transmitted by the STA in a non-HT ornon-HT duplicate format and the scrambling sequence carries the TXVECTORparameter CH_BANDWIDTH_IN_NON_HT, the TA field value is a bandwidthsignaling TA.

In an embodiment, the ACK or BA frame may be sent in HT format when aCH_BANDWIDTH parameter value of the RXVECTOR is 40 MHz. The ACK or BAframe may be sent in VHT format when CH_BANDWIDTH parameter value of theRXVECTOR is 40 MHz, 80 MHz, 160 MHz, or 80+80 MHz. The ACK or BA framemay be sent in HE format when the CH_BANDWIDTH parameter value of theRXVECTOR is 40 MHz, 80 MHz, 160 MHz, or 80+80 MHz.

The station STA transmits the response frame at the widest allowablebandwidth. When the widest allowable bandwidth is wider than a minimumbandwidth of a frequency segment, the response frame may duplicateinformation across the widest allowable bandwidth, and the responseframe may include bandwidth indicators. The response frame may include anon-HT duplicated frame.

The AP determines OFDMA sub-band CSI for a channel between the AP andthe station STA using the response frame as a sounding frame. The APthen allocates sub-bands to the stations in the BSS using the OFDMAsub-band CSI.

FIG. 21 illustrates a frame 2100 that may be used in a station-initiatedOFDMA sub-band sounding process according to an embodiment. The frame2100 may be used as the response frame in the station-initiated OFDMAsub-band sounding process 2000 of FIG. 20.

The frame 2100 is transmitted at a widest available bandwidth, which inthe embodiment of FIG. 19 is 80 MHz. The frame 2100 includes a PS-Pollframe 2118 having a bandwidth of 20 MHz, and first, second, and thirdduplicate PS-Poll frames 2112, 2114, and 2116. The PS-Poll frame 2118may include an HECE field including an OFDMA sub-band CSI report.

The first, second, and third duplicate PS-Poll frames 2112, 2114, and2116 are substantially identical in content to the PS-Poll frame 2118,and are used to duplicate the PS-Poll frame 2118 across the 80 MHzwidest allowable bandwidth of the frame 2100.

FIG. 22 illustrates a frame 2200 that may be used in a station-initiatedOFDMA sub-band sounding process according to another embodiment. Theframe 2200 may be used as the response frame in the station-initiatedOFDMA sub-band sounding process 2000 of FIG. 20.

In the embodiments related to FIG. 22, the AP and STAs take advantage ofQoS Null frame and procedure so that the AP gets the necessary sub-bandinformation over the largest bandwidth that both AP and STA operate andthe condition of the wireless medium allows. The STA sends the QoS-Nullframe in non-HT duplicate format with CH_BANDWIDTH_IN_NON_HT parameterof the TXVECTOR set to 160 MHz or 80+80 MHz when both the AP and the STAoperate with such bandwidth and secondary20, secondary40 and secondary80channels are not sensed BUSY by the STA at PIFS time before transmissionof the frame.

When the CH_BANDWIDTH_IN_NON_HT parameter of the TXVECTOR is set tolarger than 20 MHz, the TA field value is the address of the STAtransmitting the frame or a bandwidth signaling TA. When the QoS-Nullframe transmitted by a VHT or HE STA in a non-HT or non-HT duplicateformat and the scrambling sequence of the QoS-Null frame carries theTXVECTOR parameter CH_BANDWIDTH_IN_NON_HT (such as the cases describedabove), the TA field value is a bandwidth signaling TA.

The frame 2200 is transmitted at a widest available bandwidth, which inthe embodiment of FIG. 20 is 80 MHz. The frame 2200 includes a Qualityof Service (QoS) Null frame 2218, and first, second, and third duplicateQoS Null frames 2212, 2214, and 2216. The QoS Null frame 2218 mayinclude an HECE field including an OFDMA sub-band CSI report.

The first, second, and third duplicate QoS Null frames 2212, 2214, and2216 are substantially identical in content to the QoS Null frame 2218,and are used to duplicate the QoS Null frame 2218 across the 80 MHzwidest allowable bandwidth of the frame 2200.

FIG. 23 illustrates a process 2300 of determining OFDMA CSI in an AccessPoint (AP) according to an embodiment. The process 2300 may be employedin a system using the OFDMA sub-band sounding process 1800 of FIGS. 18Aand 18B, the OFDMA sub-band sounding process 2000 of FIG. 20, or both.

At S2302, the AP may transmit an indication that OFDMA sub-band soundingis to be conducted to one or more stations STAs. In another embodimentwherein a STA may initiate OFDMA sub-band sounding without an indicationfrom the AP, the AP does not transmit an OFDMA sub-band soundingindication.

At S2304, the AP receives an uplink frame suitable for use in performingOFDMA sub-band sounding (such as, for examples, one of the framesillustrated in FIGS. 17, 18, and 20) from a station. The received uplinkframe is a frame transmitted by the station at a maximum allowablebandwidth.

While receiving the uplink frame, the AP performs one or more of an RSSImeasurement, a SINR measurement, an estimate of a best MCS, and anestimate of a best NSS for each sub-band of the maximum allowablebandwidth or for each combination of the sub-band and a transmittingantenna, a receiving antenna, or both.

At S2306, the AP determines relative sub-band strengths for the stationfor each sub-band or for each sub-band/antenna combination using one ormore of the measured RSSI, the measured SINR, the estimated best MCS,and the estimated best NSS.

At S2308, the AP determines allocations of sub-bands to the station andtransmission parameters for an OFDMA downlink frame being sent to thestation according to the relative sub-band strengths for the station andthe measured data. In an embodiment, the AP allocates a sub-band in theOFDMA downlink frame to the station when a relative sub-band strength ofthe sub-band for the station is higher than a relative sub-band strengthof the sub-band to one or more other stations.

In above explanations and figures, illustrative embodiments wereprovided to allow a person of ordinary skill in the art to understandand implement embodiments of the disclosure. However, embodiments arenot limited thereto, and are therefore not limited to the number ofSTAs, specific identifications, specific formats, specific number ofSTAs per identifications, or other specifics of the illustrativeembodiments. Furthermore, while in the description and related figuresthe reference has made to one or more IEEE Std 802.11 standards, thedesign is not limited to 802.11, and a person of ordinary skill in theart in light of the teachings and disclosures herein would understandhow the present disclosures apply to any next-generation wirelessoperation that operates in licensed or unlicensed bands.

Embodiments of the present disclosure include electronic devicesconfigured to perform one or more of the operations and/or to generate,decode, or both the frames described herein. The electronic devices mayinclude wireless devices such as wireless device 200 shown in FIG. 2,including the AP 103 and stations 104 to 114 illustrated in FIG. 1.However, embodiments are not limited thereto.

Embodiments of the present disclosure may further include systemsconfigured to operate using the processes and frames described herein.The systems may include basic service sets (BSSs) such as the BSS 100 ofFIG. 1, but embodiments are not limited thereto.

Embodiments of the present disclosure may be implemented in the form ofprogram instructions executable through various computer means andrecorded in a non-transitory computer-readable medium. Thenon-transitory computer-readable medium may include one or more ofprogram instructions, data files, data structures, and the like. Theprogram instructions may be adapted to execute the processes and togenerate and decode the frames described herein when executed on adevice such as the wireless device 200 of FIG. 2.

In an embodiment, the non-transitory computer-readable medium mayinclude a read only memory (ROM), a random access memory (RAM), or aflash memory. In an embodiment, the non-transitory computer-readablemedium may include a magnetic, optical, or magneto-optical disc such asa hard disk drive, a floppy disc, a CD ROM, and the like.

While this invention has been described in connection with what ispresently considered to be practical embodiments, embodiments are notlimited to the disclosed embodiments, but, on the contrary, may includevarious modifications and equivalent arrangements included within thespirit and scope of the appended claims. Further, two or moreembodiments may be combined.

What is claimed is:
 1. A method for communication in a wireless localarea network, the method comprising: receiving a frame at a firstdevice, the frame being transmitted by a second device; determining, bythe first device using the frame, respective channel strengths for aplurality of sub-bands associated with a bandwidth of the frame;determining, by the first device, a sub-band Channel State Information(CSI) report according to the respective channel strengths, whereindetermining the CSI report includes: determining, by the first device,whether an indication of which information is to be included in thesub-band CSI report has been received from the second device; when thefirst device determines that the indication has been received from thesecond device, determining the sub-band CSI report according to thereceived indication of which information is to be included in thesub-band CSI report and the respective channel strengths for theplurality of sub-bands; when the first device determines that theindication has not been received from the second device, determining thesub-band CSI report according to a policy of the first device and therespective channel strengths for the plurality of sub-bands; receiving,by the first device, a soliciting frame that solicits a plurality ofdevices to respectively transmit a respective plurality of sub-band CSIreports in an Uplink (UL) Multi-User (MU) transmission; andtransmitting, by the first device in response to the soliciting frame,the sub-band CSI report to the second device as part of the UL MUtransmission, wherein the first and second devices communicate using aset of resources.
 2. The method of claim 1, the method furthercomprising: receiving an announcement frame transmitted by the firstdevice prior to receiving the frame, the announcement frame includingthe indication of which information is to be included in the sub-bandCSI report.
 3. The method of claim 2, wherein the announcement frameincludes a Null Data Packet Announcement (NDPA) frame, and wherein aSounding Dialog Token field of the NDPA frame indicates that the channelstrengths are for use in a subsequent OFDMA frame exchange.
 4. Themethod of claim 2, wherein the first and second devices are part of aBasic Service Set (BSS), the first device being a station and the seconddevice being an access point, and wherein the announcement frameincludes an indication that a group of one or more devices associatedwith the BSS are to determine respective channel strengths using thepre-announced frame.
 5. The method of claim 2, wherein the announcementframe includes an indication of whether the sub-band CSI report isprepared using an average of channel strengths for a sub-band acrossmultiple transmitting antennas, multiple receiving antennas, orcombinations of multiple transmitting antennas and multiple receivingantennas.
 6. The method of claim 1, wherein the sub-band CSI reportindicates the channel strength for each of a set of sub-bands of theplurality of sub-bands, and wherein the set of resources is configuredbased on the sub-band CSI report received by the second device.
 7. Themethod of claim 1, wherein the sub-band CSI report includes a combinedstrength determined using channel strengths of the plurality ofsub-bands, and wherein the set of resources is configured based on thecombined strength.
 8. The method of claim 1, wherein the sub-band CSIreport includes a channel strength measure determined using channelstrengths of the plurality of sub-bands, and wherein the set ofresources is configured based on the channel strength measure.
 9. Themethod of claim 1, further comprising: transmitting a sub-band CSIreport including a first channel strength of the channel strengths forthe sub-bands only when a previous frame received from the second deviceincludes an indication that the sub-band CSI report is to include thefirst channel strength.
 10. The method of claim 1, further comprising:transmitting the sub-band CSI report in a field of a High Throughput(HT) Control field of a Medium Access Control (MAC) frame.
 11. Themethod of claim 1, further comprising: transmitting the sub-band CSIreport in a management frame including an indication that the managementframe includes the sub-band CSI report, wherein the management frame isan Action frame or an Action No ACK frame.
 12. The method of claim 1,wherein the soliciting frame is a trigger frame.
 13. The method of claim1, wherein the bandwidth is a widest allowed bandwidth, the widestallowed bandwidth being a maximum bandwidth that can be received by thesecond device, transmitted by the first device, and sensed by the firstand second devices during active channel sensing.
 14. A first device forcommunicating in a wireless local area network, the first devicecomprising: a memory; and a processor, wherein the processor isconfigured to perform: receiving a frame at a first device, the framebeing transmitted by a second device, determining, by the first deviceusing the frame, respective channel strengths for a plurality ofsub-bands associated with a bandwidth of the frame, determining, by thefirst device, a sub-band Channel State Information (CSI) reportaccording to the respective channel strengths, wherein determining theCSI report includes: determining, by the first device, whether anindication of which information is to be included in the sub-band CSIreport has been received from the second device; when the first devicedetermines that the indication has been received from the second device,determining the sub-band CSI report according to the received indicationof which information is to be included in the sub-band CSI report andthe respective channel strengths for the plurality of sub-bands, andwhen the first device determines that the indication has not beenreceived from the second device, determining the sub-band CSI reportaccording to a policy of the first device and the respective channelstrengths for the plurality of sub-bands; receiving, by the firstdevice, a soliciting frame that solicits a plurality of devices torespectively transmit a respective plurality of sub-band CSI reports inan Uplink (UL) Multi-User (MU) transmission, and transmitting, by thefirst device in response to the soliciting frame, the sub-band CSIreport to the second device as part of the UL MU transmission; whereinthe first and second devices communicate using a set of resourcesconfigured based on the channel strength determinations made using theframe.
 15. The first device of claim 4, wherein the processor is furtherconfigured to perform: receiving an announcement frame transmitted bythe first device prior to receiving the frame, the announcement frameincluding the indication of which information is to be included in thesub-band CSI report.
 16. The first device of claim 15, wherein theannouncement frame includes a Null Data Packet Announcement (NDPA)frame, and wherein a Sounding Dialog Token field of the NDPA frameindicates that the channel strengths are for use in a subsequent OFDMAframe exchange.
 17. The first device of claim 15, wherein the first andsecond devices are part of a Basic Service Set (BSS), the first devicebeing a station and the second device being an access point, and whereinthe announcement frame includes an indication that a group of one ormore devices associated with the BSS are to determine respective channelstrengths using the pre-announced frame.
 18. The first device of claim15, wherein the announcement frame includes an indication of whether thesub-band CSI report is prepared using an average of channel strengthsfor a sub-band across multiple transmitting antennas, multiple receivingantennas, or combinations of multiple transmitting antennas and multiplereceiving antennas.